Biological samples are often obtained by a researcher or clinician for diagnostic evaluation to determine the presence of certain diseases and to determine an appropriate treatment for the disease. Common diagnostic processes for diseases include histological and cytological diagnosis. For example, tumors are typically examined for histological and cytological abnormalities.
Biological samples are also obtained for molecular diagnostic. In recent years, nucleic acid analysis, and particularly RNA and DNA analysis and studies have become common place in research for the treatment of numerous diseases. An essential requirement for accurate RNA and DNA qualitative and quantitative analysis is the presence of high quality and intact RNA and DNA. For example, intact nucleic acid is necessary for RT-PCR, Northern blot hybridization and nuclease protection assays analysis of nucleic acid expressions.
Biological samples can be obtained from various sources and by various processes. Numerous devices exist that are designed to remove a small amount of tissue from an organ or specimen. For example, small samples can be obtained using a device similar to a punch to extract core fragments of tissue. Another device for performing a biopsy uses an aspirating needle device that can extract single cells, small cell clumps and tissue fragments.
Generally, it is preferable to perform the histologic or cytologic analysis immediately after being extracted from the patient or source to obtain the most accurate results possible. Numerous molecular changes can occur in the sample during storage, which can affect the final results. For example, nucleic acids in a biological sample can undergo numerous changes, including gene transcription, and the nucleic acids readily degrade during storage at room temperature when not treated with a stabilizing agent.
The analysis of a biological sample at the time of collection is often impossible or not practical. Therefore, it is necessary to store the sample under controlled conditions to prevent or inhibit degradation of the tissue components and to retain the integrity of the results of the analysis. Biological samples are typically stored in a container with a suitable fixative reagent. A typical fixative reagent is 10% formaline. Other fixatives include water miscible alcohols, ethanol/acetone mixtures, and ethanol/acetic acid mixtures. Ammonium sulfate solutions have also been used as disclosed in U.S. Pat. No. 6,204,375 to Lader, which is hereby incorporated by reference in its entirety. The containers with the biological sample in the fixative reagent can then be sent to a pathology laboratory or other destination for analysis.
Proper handling of the biological sample is essential for accurate nucleic acid analysis, and particularly for RNA quantitative and qualitative evaluation. The biological samples require an effective amount of the fixative reagent to preserve the sample. In addition, some reagents require that the sample be completely covered with the fixative reagent to ensure effective preservation. Typically, the biological samples are simply placed in a small container for storage. The biological samples which can be very small can be difficult to locate and recover from the container.
To obtain high quality test results from biological specimens, early stabilization or preservation of the sample may be required. Biological samples and other cells can be quick frozen by various methods as known in the art. Specimens for anatomical pathology are typically preserved in formaldehyde and alcohol based solutions. Specimens for molecular testing have been preserved in these and other reagents, such as chaotropic salts.
Quick freezing of biological samples can be effective in stabilizing cellular and molecular characteristics. Samples are typically transported on dry ice. Quick freezing, however, is not always available or convenient. Typically, the collection location and processing laboratory are separated in location and time, which creates an impediment to stabilization.
The prior methods and containers for storing, transporting and stabilizing biological samples have experienced some success for the intended purposes, but have several known limitations. There is, however, a continuing need in the industry for an improved container and method for storing biological samples.